1. Field of the Invention
The invention relates to the field of detection of analytes using electromagnetic detection.
2. Description of the Related Art
Recently, novel molecular-level detection schemes have attracted great interest in many fields, such as biology, chemistry and applied physics. However, most currently developed detection methods rely on first attaching certain sensing tags onto the target molecules and then detecting the presence of these tags to indirectly infer the information about the target molecules. A common example of such is a fluorescent tags attached to the target molecules. However, label-tagging processes required by currently developed detection methods thus introduce several impediments described as follows.
First of all, the label-tagging processes normally require several chemical steps which complicate the design and operation of the sensor system and fundamentally limit the sensor integration level. Also those chemical steps could be time-consuming and lead to prolonged sensing time. This significantly limits the total throughputs of the sensor system per given time.
Secondly, these label-tagging processes can degrade the sensor accuracy, since only a limited tagging efficiency (instead of 100%) can be achieved practically. This means that some of the target molecules will not be tagged with the labels and therefore cannot be sensed by the sensors, resulting in “false negative” detection errors. Also free labels with no target molecules may also remain in the samples after the tagging process, which will be detected by the sensor and lead to “false positive” detection errors.
Moreover, the attached labels will inevitably alter the chemical and/or physical properties of the target molecules. For example, the chemical dynamics and the physical diffusion properties of the target molecules can be dramatically changed when attached to certain molecular tags. These include the cases when the tags are of large molecular mass and/or excessive electrical charge and/or certain hydrophilic/hydrophobic properties. This interference effect due to the labels therefore inhibits further studies of the target molecules.
Furthermore, those molecular labels and their corresponding buffers could be costly when used in large quantities. And for each complete operation of the sensor, those molecular labels and their corresponding buffers are used as consumables and needed to be replenished. This is exacerbated in high throughput parallel sensing, commonly performed in today's bioassays. Therefore, the system cost may be significantly increased due to the labels and buffers.
Improved techniques for detection of molecules are clearly needed, including techniques that do not require labeling of the target molecules.